JP2007234234A - Discharge tube lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure timing up to a stable arc discharge while reducing a time until the stable arc discharge. <P>SOLUTION: A discharge tube lighting device executes lighting control by supplying power to a discharge tube. A control means (a microcomputer 81 of a control circuit 8) has a first power supply pattern, in which relatively large power is supplied in a negative resistance region of inter-electrode voltage characteristics of the discharge tube to an elapsed time immediately after lighting of the discharge tube; and a second power supply pattern for supplying power corresponding to output power characteristics to an inter-electrode voltage after passing the negative resistance region. The lighting control is executed by supplying power to the discharge tube while switching between the first/second power supply patterns after being triggered by the passing of the negative resistance region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge tube lighting device, and more particularly to a discharge tube lighting device that performs lighting control of a mercury-free high-intensity discharge tube suitable for use in a vehicle headlight.

  A bright, long-life, low-power, high-intensity discharge tube (hereinafter referred to as a HID (High Intensity Discharge) bulb) is widely used as a vehicle headlight. In recent years, in consideration of the disposal environment, a type of HID valve (hereinafter referred to as a mercury-free valve) that does not use mercury enclosed in a conventional HID valve (hereinafter referred to as a conventional valve) has been developed. Practical use has also begun as an in-vehicle headlight.

The above-described conventional bulb is filled with a metal halide such as xenon gas, mercury, sodium, scandium, and the light emission sequence is as described below.
That is, when the bulb concentration at the time of lighting is low, only the gas, xenon gas, emits light, and mercury with a low boiling point close to room temperature evaporates as the temperature rises due to the supply of lighting power, increasing the amount of light emission. Then, the temperature of the bulb is further increased by the supplied lighting power, and the metal halide (sodium, standium) having a boiling point higher than that of mercury evaporates, and the light emission amount further rises to reach the rated light emission amount.

In addition, the luminous efficiency of the xenon gas described above is low, and the luminous efficiency of sodium and scandium is high. On the other hand, since the luminous efficiency of mercury is between xenon gas and sodium or scandium, the rapid evaporation (emission) of metal halide can be mitigated by enclosing mercury.
In accordance with the above-described light emission sequence, sequentially evaporating each metal halide to be encapsulated as the temperature of the HID bulb increases is advantageous in terms of smoothing and rapidly increasing the light emission amount of the HID bulb.

However, the mercury-free bulb only emits xenon gas with low luminous efficiency for a few seconds until the metal halide evaporates after lighting, and therefore a sufficient amount of light emission cannot be obtained.
In a mercury-free bulb, in order to obtain a sufficient amount of light emission quickly, it is necessary to increase the power supplied immediately after lighting, increase the light emission by the xenon gas having a low light emission efficiency, and at the same time promote the evaporation of the metal halide. However, the large supply power immediately after lighting becomes excessive power when the metal halide evaporates and light emission starts. Therefore, the supply power is attenuated according to the evaporation of the metal halide, and the rated power is reached while keeping the light emission amount constant. Therefore, it is necessary to perform power supply control with good responsiveness corresponding to a change in the amount of light emission of the metal halide that increases rapidly.

For this reason, many techniques for appropriately controlling the amount of light emission that changes rapidly when a mercury-free bulb is used have been proposed.
For example, a technique for smoothing the light emission amount by capturing the timing at which the metal halide evaporates based on the voltage immediately after the mercury-free bulb is turned on and the amount of change in the voltage thereafter, and controlling the supply power (for example, see Patent Document 1). The light emission efficiency increase detection means detects that the amount of light emission suddenly increases as the metal halide evaporates and emits light, and the supplied power is attenuated by the detection by the light emission efficiency increase detection means to provide a stable and smooth light emission quantity. Technology to obtain (see, for example, Patent Document 2), correct voltage drop due to components intervening in the mercury-free bulb, detect accurate bulb voltage, and supply large electric power immediately after lighting, that is, energization of a large current A technique (see Patent Document 3) that performs appropriate power control by supplying appropriate power is sometimes known.

JP 2003-338930 A (paragraphs “0011” to “0018”, FIG. 3) JP 2004-119164 A (paragraphs “0007” to “0011”, FIG. 1) Japanese Patent Laying-Open No. 2005-1000094 (paragraph “0024” to “0033”, FIG. 3)

Conventional discharge tube (mercury-free bulb) lighting devices, as disclosed in Patent Documents 1 to 3 described above, emit bright light by evaporating metal halide from the time when only a dark xenon gas emits light with a small amount of light emission. Until the start timing is detected and the power is attenuated, the maximum power is supplied to the HID valve.
In addition, when the lamp is turned on for a short time and then turned on again, sufficient residual heat remains in the HID bulb. In this case, the metal halide may remain evaporated, which is commensurate with the amount of evaporation of the already evaporated metal halide. Power is being supplied.

According to the background art having the power supply pattern described above, the power supply pattern is controlled depending on the presence or absence of evaporation of the metal halide. However, different power supply patterns require different control factors.
For example, in the former lighting from the state before the metal halide evaporates, in order to detect the timing of the sudden light emission change due to the evaporation of the metal halide, the interelectrode voltage in the light emission by the xenon gas immediately after the lighting is used as a reference value. It is necessary to secure. Further, in the latter case of lighting from a state where the metal halide has already evaporated, it is necessary to measure the turn-off time of the HID bulb in order to supply power corresponding to the evaporation amount of the metal halide according to the temperature of the HID bulb due to residual heat. There is.

However, the estimation of the temperature of the HID bulb based on the turn-off time means that, for example, the heat insulation and heat dissipation state varies depending on the structure of the headlight to which the HID bulb is attached, and the influence of wind, temperature and engine heat generation while the vehicle is running. Therefore, it cannot be said that there is a perfect correlation between the turn-off time and the temperature of the HID bulb due to residual heat, and only rough control using representative values is possible at present.
In order to accurately grasp the temperature of the HID valve and further the degree of evaporation of the metal halide, it is preferable to measure the voltage between the electrodes of the HID valve.

Therefore, the parameters necessary for power control for quickly emitting a sufficient amount of light emission are collected in the voltage between the electrodes of the bulb immediately after lighting.
However, the mercury-free bulb immediately after lighting, from the state of dielectric breakdown caused by supplying a high voltage to start lighting the mercury-free bulb, increases the current through the glow discharge with a small current, Follow the process leading to arc discharge that overheats xenon gas. In each of these processes, there is a voltage of about 25 KV due to dielectric breakdown, a voltage of several tens of volts due to stable arc discharge, and a voltage due to glow discharge between them, and the voltage between the electrodes of the mercury-free valve depends on these states. Each state becomes clear because it changes.

Since the conventional bulb shifts to a stable arc discharge in a short time even with a small amount of supply power due to the amount of mercury contained, it is possible to easily detect the timing of the arc discharge resulting in a stable interelectrode voltage. It was easy to estimate the state of the valve by measuring the voltage between the electrodes of the valve.
In contrast, the mercury-free bulb has a large electrode diameter for energization with a large current (0.8A for the mercury-free bulb compared to the rated current of 0.4A for the conventional bulb), and secures the light emission immediately after lighting. Therefore, the heat capacity of the bulb is increased by enclosing a large amount of xenon gas and enclosing a large amount of metal halide to compensate for the amount of light emitted by mercury. Therefore, the time until stable arc discharge is longer than that of the conventional bulb, and if power is insufficient during this period, the time is further extended.

In the case of lighting from the state immediately before the metal halide evaporates, when the voltage between the electrodes of the mercury-free bulb is measured after a fixed time has elapsed since lighting, depending on the individual difference of the mercury-free bulb, before the transition to arc discharge. There is a possibility to measure the mercury-free bulb-to-electrode voltage in the glow discharge and the incomplete arc discharge before the electrode is sufficiently heated.
In that case, in addition to the voltage drop due to xenon gas, it contains an unstable discharge voltage due to insufficient discharge, and it is not an accurate voltage between the bulb electrodes immediately after lighting, so if this voltage value is used as a reference, evaporation of the metal halide The timing of the voltage (light emission amount) change due to is erroneously detected, and as a result, there is a situation where the light emission amount is excessive or insufficient.

In addition, even when lighting from a state where the metal halide has already evaporated, the time to reach a stable arc discharge varies depending on the evaporation state of the metal halide, so the timing for measuring the mercury-free valve electrode voltage immediately after lighting is appropriate. Otherwise, the exact mercury-free valve condition cannot be ascertained and, therefore, an inappropriate output power may be supplied.
For example, if the above timing is too early, the voltage between the electrodes of the high mercury-free bulb at the time of glow discharge is measured, so it is assumed that the temperature of the mercury-free bulb is high. become. Conversely, if the timing is too late, the residual heat of the mercury-free valve is high, and when the amount of metal halide has already evaporated and the supply power is reduced, power is supplied in excess of the amount of metal halide evaporation. Become.

  As described above, the measurement of the voltage between mercury-free valve electrodes to quickly grasp the state of the mercury-free valve without being affected by the environment in which the mercury-free valve is used leads to stable arc discharge. Timing needs to be measured accurately.

  The present invention has been made to solve the above-described problems, and can accurately measure the timing to reach a stable arc discharge and reduce the time to reach a stable arc discharge. It aims at providing a discharge tube lighting device.

  A discharge tube lighting device according to the present invention includes a first power supply pattern for supplying relatively large power in a negative resistance region immediately after lighting of an electrode voltage characteristic with respect to an elapsed time of the discharge tube, and passing through the negative resistance region. And a second power supply pattern for supplying power corresponding to output power characteristics with respect to the interelectrode voltage, and the first and second power supply patterns are triggered by passage through the negative resistance region. Control means for switching and supplying electric power to control lighting of the discharge tube.

  According to the present invention, by switching from the first power supply pattern that supplies large power at the boundary of passing through the negative resistance region immediately after lighting to the second power supply pattern that supplies power according to the output power characteristics. The discharge tube lighting control can be performed accurately and quickly without being affected by the use environment.

Embodiment 1 FIG.
Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a bulb voltage characteristic with respect to an elapsed time of a discharge tube used in Embodiment 1 of the present invention. FIG. 2 is a graph showing the output power characteristics with respect to the voltage between the bulb electrodes of the discharge tube used in the first embodiment of the present invention.
Both FIG. 1 and FIG. 2 show the characteristics of a conventional bulb as a discharge tube, and (b) compares the characteristics of a mercury-free bulb. In both FIG. 1 and FIG. 2, the thick arrows indicate the transition of the voltage between the valve electrodes and the output power (current) during cold start and hot start.
Hereinafter, with reference to the characteristic diagrams of FIGS. 1 and 2, the background to the present invention and the general operation of the first embodiment of the present invention will be described.

  According to Embodiment 1 of the present invention, the comparison is made in the negative resistance region (from the state of dielectric breakdown to the lowest valve electrode voltage) immediately after the lighting of the voltage characteristics between the electrodes with respect to the elapsed time of the mercury-free valve. A first power supply pattern for supplying a large amount of power, and a second power for supplying power corresponding to the output power characteristic with respect to the voltage between the valve electrodes from the lowest voltage between the valve electrodes after passing through the negative resistance region to steady lighting The power supply pattern is selected, the power supply pattern is switched by the passage of the negative resistance region, the output power characteristic is selected, and the output power is controlled.

Specifically, as shown in FIG. 1 (a) and FIG. 2 (a), according to the conventional bulb, at the time of cold start in which lighting is started in a state where the electrode is cold, Less power is required to reach a stable arc discharge that reaches the lowest valve electrode voltage (negative resistance region), and the time to arc discharge is relatively low, 0.5 seconds to 1 second. short. Accordingly, it is possible to perform lighting control using output power characteristics with respect to one type of voltage between the valve electrodes. Similarly, in the hot start in which re-lighting is performed with a short turn-off time in between, lighting control can be performed using output power characteristics with respect to one type of voltage between the bulb electrodes.
In hot start, after a short light extinction, the metal halide remains as a vapor due to residual heat, and the electrode temperature is hard to decrease, and the residual heat also remains in the electrode, so it is easy to preserve the internal state of the conventional valve. If power is supplied using the output power characteristic with respect to the voltage between the bulb electrodes for normal lighting, it is possible to reach a stable arc discharge in which the lowest voltage is reached in a short time. Accordingly, the temperature state of the valve can be grasped in a short time, and therefore, an appropriate output power can be determined and lighting control can be performed.

On the other hand, in the mercury-free valve, as with conventional valves, when lighting control is performed using the output power characteristics for one type of valve electrode voltage, the mercury-free valve has a larger heat capacity than conventional valves and emits thermoelectrons. In order to overheat to a possible temperature, relatively large electric power is required, so that the time until a stable arc discharge at which the voltage between the bulb electrodes immediately after lighting becomes the lowest voltage is extended (1-2 seconds). As a result, the time until a sufficient amount of light emission is obtained is delayed.
The time to reach a stable arc discharge state where the voltage between the bulb electrodes is the lowest depends on the supplied power, and is short for high power and extended for low power. From this, in order to grasp the temperature state of the mercury-free valve in a shorter time, apart from the output power characteristics of the conventional valve with low output power with respect to the voltage between the valve electrodes, for high power supply that heats the valve electrode early It is preferable to prepare output power characteristics with respect to the voltage between the valve electrodes and to control the output power according to the output power characteristics with respect to two kinds of valve electrode voltages.

In other words, immediately after the mercury-free bulb is turned on, first, a large amount of power is supplied to reach the arc discharge that quickly reaches the lowest voltage (Vmin), and the state of the bulb (cold start / hot start) is detected at that timing. Then, it is preferable that output power suitable for the state of the valve at that time is supplied to perform appropriate power control until steady lighting.
1 (b) and 2 (b), after a short turn-off (hot start), as indicated by a thick arrow, the transition of the voltage between the valve electrode and the output power during the cold start of the mercury-free valve and the hot start is indicated by a thick arrow. However, as long as the current state of the valve is grasped by stabilizing the temperature of the metal halide vapor and electrode remaining after supplying high power (stable arc discharge at the lowest voltage Vmin '), it is appropriate as with conventional valves. Power can be determined, and output power control can be performed. As a result, the amount of light emission can be increased rapidly, and light emission characteristics preferable as a headlight can be obtained.

In Embodiment 1 of the present invention, when the amount of change in voltage is negative in the voltage between the valve electrodes from the state of dielectric breakdown to steady lighting, the characteristics of the output power with respect to the voltage between the valve electrodes for large power are obtained. Use to control the output power.
Specifically, FIG. 2B shows a state where the voltage change is negative, and a state where switching from a high power output of 70 W to a 35 W output for steady lighting is performed by a thick arrow. That is, in the dielectric breakdown state immediately after lighting, the glow discharge state, and the process leading to arc discharge in which the voltage between the bulb electrodes becomes the lowest value Vmin (negative resistance region), the voltage between the bulb electrodes decreases. In the process of steady lighting after passing, the state of the gas sealed in the bulb changes and the voltage rises. Accordingly, since the stable arc discharge has not yet been reached while the voltage between the bulb electrodes is decreasing, 70 W can be supplied to heat the electrode, so that a stable arc discharge state can be reached at an early stage. As a result, the amount of light emission can be increased rapidly, and light emission characteristics preferable as a headlight can be obtained.

Further, in the first embodiment of the present invention, in the voltage between the valve electrodes from the state of dielectric breakdown to steady lighting, the amount of change in the voltage changes from negative to positive at the timing between the valve electrodes for high power output. The output power characteristic for the voltage (first power supply pattern) is switched to the output power characteristic (second power supply pattern) for the voltage between the bulbs for normal lighting, and the output power is controlled.
Specifically, as shown in FIG. 2B, in the discharge tube lighting device according to Embodiment 1 of the present invention, the amount of change in the voltage between the bulb electrodes is negative to positive in both the cold start and the hot start. It is determined that a stable arc discharge state in which the voltage between the bulb electrodes is the lowest voltage value is reached. Then, the temperature of the electrode is estimated from the voltage between the electrodes of the valve at this timing, and when it is determined to be hot start, the output power characteristic is switched from 70 W to 35 W for normal lighting. As a result, a stable arc discharge state can be reached at an early stage, and the amount of light emission can be increased quickly, and light emission characteristics preferable as a headlight can be obtained.

Further, in the first embodiment of the present invention, in the voltage between the valve electrodes from the state of dielectric breakdown to steady lighting, the amount of change in the voltage changes from negative to positive at the timing between the valve electrodes for high power output. When switching from the output power characteristic (first power supply pattern) to the voltage to the output power characteristic (second power supply pattern) to the voltage between the bulbs for normal lighting, the output power is attenuated and smoothed according to the elapsed time. To control the output power.
Specifically, as shown in FIG. 2 (b), when a stable arc discharge state is reached, when switching from 70W output power to low power output power suitable for the valve at that time, step by step. The output power is smoothly reduced and finally attenuated to a rated power of 35W. As a result, the change in the light emission amount is smoothed so as not to cause flickering.

Hereinafter, the configuration and operation of the discharge tube lighting device according to Embodiment 1 of the present invention will be described in detail with reference to FIG.
FIG. 3 is a hardware block diagram showing the internal configuration of the discharge tube lighting device according to Embodiment 1 of the present invention.

  In FIG. 3, a DC power source 1 such as a vehicle battery is connected to an input terminal of a DC booster circuit (DC / DC converter) 2, and the DC boosted by the DC booster circuit 2 is connected to a DC-AC inverter 3. ing. The output terminal of the DC-AC inverter 3 is connected to an activation circuit 4 that applies a high voltage pulse for activation when the mercury-free valve 5 is activated. The DC-AC inverter 3 and the DC-AC inverter 3 together with the DC-AC inverter 3 are mercury-free. A lighting circuit of the bulb 5 is configured.

The connection path between the DC booster circuit 2 and the DC-AC inverter 3 is provided with a current detection circuit 6 for detecting current. Here, the output current of the DC booster circuit 2 is detected and controlled by a current detection element. This is supplied to a microcomputer 81 that is a control center of the circuit 8. Further, a voltage detection circuit 7 for detecting a voltage is provided between the connection path between the DC booster circuit 2 and the DC-AC inverter 3. Here, the output voltage of the DC booster circuit 2 is detected by a voltage detection element. Then, it is supplied to the microcomputer 81 which becomes the control center of the control circuit 8.
The control circuit 8 is composed of, for example, a dedicated control IC chip. On this chip, a lighting control circuit 82 composed of CMOS transistors, an EEPROM 83, a microcomputer 81 with a built-in ROM / RAM serving as a control center, and the like are mounted. Has been.

In the configuration described above, the microcomputer 81 serving as the control center of the control circuit 8 follows the control program recorded in the built-in ROM in advance, and the voltage between the electrodes of the mercury-free valve detected by the voltage detection circuit 7 (hereinafter simply referred to as the valve voltage). ) Is output to the lighting control circuit 82, and the lighting control circuit 82 outputs the output power to the lighting circuit based on the set value and the detected value of the valve current detected by the current detection circuit 6. Control.
The microcomputer 81 also assigns a work area to the built-in RAM or the EEPROM 83 according to the control program recorded in the built-in ROM, and is relatively large in the negative resistance area immediately after the lighting of the voltage characteristics between the electrodes with respect to the elapsed time of the mercury-free valve 5. The power supply pattern A for supplying power and the power supply pattern B for supplying power corresponding to the output power characteristic with respect to the interelectrode voltage after passing through the negative resistance region are switched when triggered by the passage through the negative resistance region. It supplies to the lighting control circuit 82 and functions as a control means for performing lighting control of the mercury-free valve 5. Details will be described later.

FIG. 4 is a block diagram showing a functional development of the internal configuration of the microcomputer 81 that implements the control means of the present invention in the control circuit 8 shown in FIG.
The internal configuration of the microcomputer 81 is roughly divided into a voltage change amount detection unit 811, an output power supply pattern selection output unit 812, an output power supply amount control unit 813, and a lighting control unit 814. In FIG. 4, blocks indicated as A and B are a first power supply pattern for supplying relatively large power in the negative resistance region immediately after lighting of the voltage characteristics between the electrodes with respect to the elapsed time of the mercury-free valve 5, negative Each of the 2nd electric power supply pattern which supplies the electric power according to the output electric power characteristic with respect to the voltage between electrodes after passing through a resistive region is shown.

The voltage change amount detection unit 811 has a function of calculating a change amount (ΔV / dt) of the interelectrode voltage in the mercury free valve 5 measured each time by the voltage detection circuit 7 and outputting the change amount to the output power supply pattern selection output unit 812. Have.
The output power supply pattern selection output unit 812 includes a first power supply pattern A that supplies relatively large power in the negative resistance region immediately after lighting of the interelectrode voltage characteristics with respect to the elapsed time of the mercury-free valve 5, and a negative power supply pattern A. And a second power supply pattern B that supplies power according to the output power characteristics with respect to the voltage between the valve electrodes after passing through the resistive region, and the amount of change in the interelectrode voltage calculated by the voltage change amount detector 811 ( When ΔV / dt) is determined to be “negative”, the lighting control unit 814 has a function of supplying output power based on the first power supply pattern A. The output power supply pattern selection output unit 812 also changes the power supply pattern from A to the second power supply when it is determined that the change amount (ΔV / dt) of the interelectrode voltage has changed from “negative” to “positive”. There is a function of switching to pattern B and outputting power based on the power supply pattern to the output power amount control unit 813.

The output power supply amount control unit 813 relates to the supply of output power to the lighting control unit 814, and when the output power supply pattern selection output unit 812 switches from the first power supply pattern A to the second power supply pattern B, the elapsed time It has the function to perform attenuation control sequentially according to. At this time, the output power supply amount control unit 813 may sequentially change the output power supply amount for attenuation in accordance with the elapsed time. Details will be described later.
The lighting control unit 814 turns on the mercury-free valve 5 via the lighting control circuit 82 based on the power supply pattern output via the output power supply pattern selection output unit 812 or the output power supply amount control unit 813. It has a function to supply power necessary for control.

FIG. 5 is a flowchart cited for explaining the operation of the discharge tube lighting control apparatus (microcomputer 81) according to Embodiment 1 of the present invention.
Hereinafter, the operation of the discharge tube lighting device according to Embodiment 1 of the present invention will be described in detail with reference to the flowchart shown in FIG.

The microcomputer 81 first detects power-on in accordance with the control program recorded in the built-in ROM (step ST501), and then, for example, the mercury-free valve 5 mounted on the vehicle with respect to the lighting circuit (starting circuit 4 in FIG. 3). Control is performed to apply a high voltage pulse “ignition (IGN pulse)” for lighting up (step ST502).
Thereafter, the microcomputer 81 always reads the voltage between the valve electrodes of the mercury-free valve 5 measured by the voltage detection circuit 7 (step ST503), and controls the output power described below.

Specifically, the voltage change detection unit 811 calculates the change (ΔV / dt) from the current value and the previous value of the voltage between the valve electrodes of the mercury-free valve 5 that is measured and read by the voltage detection circuit 7 each time. Is output to the output power supply pattern selection output unit 812 (step ST504).
The output power supply pattern selection output unit 812 constantly monitors the change amount (ΔV / dt) of the voltage between the valve electrodes calculated by the voltage change amount detection unit 811 (step ST505), where the valve voltage decreases. If it is determined to be “negative” (step ST505 “down”), the power value of “70 W” based on the first power supply pattern A is set to the variable Pn as the current value for the lighting control unit 814 (step ST505). ST506), and outputs to lighting control unit 814 (step ST507).

  On the other hand, the output power supply pattern selection output unit 812 has detected that the change amount (ΔV / dt) of the interelectrode voltage has changed from “negative” to “positive” in the monitoring process of the voltage between the electrodes in step ST505. Sometimes (step ST505 "rising") to switch the power supply pattern to the output power characteristic (second power supply pattern B) with respect to the voltage between the bulb electrodes for steady lighting, the target of "35W" according to that characteristic The power value is set to variable Pm and output to output power amount control section 813 (step ST508).

As a result, the output power amount control unit 813 compares the power value previously set in the variable Pm, which is the target of power attenuation, with the currently supplied power value set in the variable Pn (Step S13). ST509) Here, as long as it is determined that Pn> Pm where the current value is higher than the target value, the variable Pn is updated to a value obtained by subtracting the attenuation amount X set to perform attenuation step by step (step ST509). In step ST510, electric power according to the obtained Pn is supplied to the lighting control unit 814 (step ST507).
On the other hand, when the current value set in the sequentially updated variable Pn becomes equal to the target value (35 W) set in the variable Pm, the output power amount control unit 813 sets the current value set in the variable Pm to the current value set in the variable Pm. Based on the power (35 W), the lighting control unit 814 is supplied (step ST510).

The lighting control unit 814 is connected to the mercury-free valve via the lighting control circuit 82 based on the power supply patterns Pm and Pn-X output via the output power supply pattern selection output unit 812 or the output power supply amount control unit 813. The electric power required for the lighting control of 5 is supplied.
Note that the variable X set as the amount of attenuation by the output power amount control unit 813 is variable. For example, it may be possible to subtract the previous power amount by 1/2 according to the elapsed time to generate the value. It is done. As a result, the light emission amount of the mercury-free bulb 5 can be smoothly changed and controlled so as not to flicker.

As described above, in the present invention, in order to grasp the state of the mercury-free valve 5 quickly and accurately, the timing to reach a stable arc discharge is accurately measured, and the time to reach a stable arc discharge is determined. In order to shorten the distance, a correlation for arc discharge stabilization is used in addition to the correlation with the output power with respect to the voltage between the valve electrodes, which is one type in the conventional valve.
According to the present invention, in the voltage between the valve electrodes from the state of dielectric breakdown to steady lighting, the voltage change amount changes from negative to positive (passing through the negative resistance region), for high power output. The output power characteristic (first power supply pattern) with respect to the voltage between the valve electrodes is switched to the output power characteristic (second power supply pattern) with respect to the voltage between the bulb electrodes for normal lighting, and the output power is controlled. This makes it possible to avoid instability in output power control of a conventional discharge tube lighting device that estimates the bulb temperature and state by measuring the turn-off time, or variations due to the structure and temperature change of the individual headlights to be mounted. It is possible to perform discharge tube lighting control by accurate and quick output power control without being affected by the use environment.

It is a figure which shows the Halve voltage characteristic with respect to the elapsed time of the discharge tube used in Embodiment 1 of this invention. It is a figure which shows the output electric power characteristic with respect to the voltage between valve electrodes of the discharge tube used in Embodiment 1 of this invention. It is a hardware block diagram which shows the internal structure of the discharge tube lighting device which concerns on Embodiment 1 of this invention. It is the block diagram which expanded and showed the function of the internal structure of the microcomputer which implement | achieves the control means of this invention among the control circuits shown in FIG. It is the flowchart quoted in order to demonstrate operation | movement of the discharge tube lighting device (microcomputer) which concerns on Embodiment 1 of this invention.

Explanation of symbols

1 DC power supply, 2 DC booster circuit, 3 DC-AC inverter, 4 start-up circuit, 5 mercury-free valve, 6 current detection circuit, 7 voltage detection circuit, 8 control circuit (control means), 81 microcomputer, 82 lighting control circuit, 83 EEPROM, 811 Voltage change amount detection unit,
812 output power supply pattern selection output unit, 813 output power supply amount control unit, 814 lighting control unit.

Claims (5)

A discharge tube lighting device for controlling lighting by supplying power to a mercury-free discharge tube,
A first power supply pattern for supplying relatively large power in the negative resistance region immediately after lighting of the interelectrode voltage characteristic with respect to the elapsed time of the discharge tube, and an output for the interelectrode voltage after passing through the negative resistance region A second power supply pattern that supplies power according to power characteristics, and switches between the first and second power supply patterns upon passing through the negative resistance region to supply power, and the discharge A discharge tube lighting control device comprising a control means for performing tube lighting control. The control means includes
A change amount of the interelectrode voltage in the discharge tube is calculated, and when the change amount is determined to be negative, output power is supplied to the discharge tube based on the first power supply pattern, and the discharge tube 2. The lighting control device for a discharge tube according to claim 1, wherein lighting control is performed. The control means includes
The amount of change in the voltage between the electrodes in the discharge tube is calculated, and when it is determined that the amount of change has changed from negative to positive, output power is supplied to the discharge tube from the first power supply pattern. 3. The discharge tube lighting control device according to claim 1, wherein the discharge tube lighting control is performed by switching to a power supply pattern of 2. The control means includes
4. The discharge tube lighting device according to claim 3, wherein when the output power is supplied to the discharge tube from the first power supply pattern to the second power supply pattern, the attenuation control is sequentially performed according to the elapsed time. . The control means includes
5. The discharge tube lighting device according to claim 4, wherein the amount of output power supplied for attenuation is sequentially changed according to elapsed time.

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